New electrode materials are required for the rapid development of high energy and high power devices. Amongst promising positive electrode material for Li-ion batteries, lithium iron phosphate has been proposed as a replacement for the currently used layered materials. Practical use in large batteries is hindered by a poor lifetime at elevated temperature and lower available energy due to a relatively low cell voltage. Here, our objective is to develop an improved phosphate cathode material with voltage higher than LiFePO4 (3.4 V), based on LiMnPO4 (4.1 V) and partially substituted materials. The challenges include increasing the available energy through higher voltage, without decreasing power, and reaching the safety level of LiFePO4 in overcharge. This industrial research project is funded under the ANR Stock-E programme (PHOSPHALION 2009-2012) with theoretical and experimental fundamental aspects developed by the academic partners. In Li-ion anode materials, three lithium-storage mechanisms dominate: insertion, alloying and conversion reactions. To reach the high energy density required for electric vehicle applications, a second aspect of our research is dedicated to the investigation of conversion materials as negative electrodes. These are based on intermetallic or composite materials involving phosphorus, tin or antimony. Study of electron and ion transfer mechanisms is required for better understanding of problems related to volume changes, side-reaction with electrolyte, relaxation processes limiting reaction kinetics, and premature ageing. These effects were considered in the ANR ANECDOTE project (2007-2010), where novel synthesis methods were proposed for elaboration of Sn/BPO4 composites. Lithium reaction mechanisms in tin intermetallic based electrodes with nano- and micro-sized particles are investigated using theoretical and experimental methods in a joint project with the ALISTORE-ERI, funded by CNRS Energy 2. In parallel, nanostructuring of phosphide and antimonide electrodes is being developed using various deposition techniques. The study of reaction mechanisms at interfaces in particular related to passivation layers and electrolyte reduction is also programmed. Integration of Li-ion batteries specifically adapted for the storage of photovoltaic energy in isolated sites is being developed in collaboration with the lnstitut Electronique du Sud, UM2, with funding from UM2’s Pluridisciplinary research Programme, priority research area "Energy".

Use of specific probe techniques is the keystone of the above projects. At the microscopic level the phenomena are analysed using techniques in which AIME scientists are internationally recognised or have specific expertise: Mössbauer spectrometry, X-ray diffraction and ab initio calculations. One aim is to develop a quantitative approach to the analysis of Mössbauer and NMR spectra through the modelling of hyperfine interactions. Mössbauer spectrometry is used to follow modifications in electronic structure associated with defects and interface phenomena in electrode materials during insertion/de-insertion of lithium. These investigations contribute to the ALISTORE-ERI network.

In situ and operando measurements are being further developed in an ambitious programme to further the understanding of the behaviour of battery materials during operation. These aspects were already initiated within ANR-Blanc LINEMBIS (2007-2010) and will be further developed by combining X-ray absorption, Mössbauer and NMR spectroscopies. These studies go beyond battery materials use, being fully applicable to catalytic materials for reforming (collaboration with IFP) and nuclear waste storage materials for environmental protection (collaboration CEA).